Molecular cloning of the human gene STK10 encoding lymphocyte-oriented kinase, and comparative chromosomal mapping of the human, mouse, and rat homologues.

LOK is a new and unique member of the STE20 family with serine/threonine kinase activity, and its expression is restricted mostly to lymphoid cells in mice. We cloned the cDNA encoding the human homologue of LOK. The amino acid sequence deduced from the cDNA shows a high similarity to that of mouse LOK, with 88% identity as a whole. The kinase domains at the N-terminus and the coiled-coil regions at the C-terminus are particularly conserved, showing 98% and 93% identity, respectively. Western blot analysis with mouse LOK-specific antibody detected 130 000 Mr LOK proteins in human and rat lymphoid cell lines and tissues. The gene encoding the LOK (STK10/Stk10) gene was mapped by fluorescence in situ hybridization to chromosome 5q35.1 in human, chromosome 11A4 in mouse, and chromosome 10q12.3 in rat. By virtue of polymorphic CA repeats found in the 3' untranslated region of the mouse Stk10 gene, the Stk10 locus was further pinpointed to chromosome 11 between D11Mit53 and D11Mit84, using the intersubspecific backcross mapping panel. These results established STK10 as a new marker of human chromosome 5 to define the syntenic boundary of human chromosomes 5 and 16 on mouse chromosome 11.